Neutron source localization and identification using passive real-time collection of the neutron source emissions requires measurement and comparison of distinguishing features from the given neutron emitting source. Distinguishing features at or greater than one meter (i.e., not primary beta or alpha particles) include x-rays, gamma-rays, and/or neutrons, although one normally only measures the photon intensity, photon energy spectrum, neutron intensity, or neutron energy spectrum. Current instruments merely individually measure quantities proportional to the neutron energy spectra or photon energy spectra from the neutron source. These systems lack accuracy, precision and portability. Therefore, it would be desirable to provide an apparatus and method for curing the shortcomings of current instruments such as those of the identified above.